Cardiac trauma and third degree AV block in a dog following a road accident.

A nine-and-a-half-year-old dog was referred for investigation of bradycardia after being hit by a car. Electrocardiography revealed a third degree atrioventricular (AV) block. The dog died during a syncopal attack. Post mortem examination revealed an atrial septal tear with haemorrhage and myocardial degeneration affecting the AV bundle.